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Nerve Entrapment and Compression Disorders

Essentials

  • Entrapment neuropathy, i.e. peripheral nerve entrapment, means that the nerve is compressed between surrounding anatomical structures. The pressure is usually persistent, although its severity may vary according to the extent of tissue oedema and strain on the limb.
    • In order to recover completely, entrapment neuropathies generally require treatment (reduction of the oedema, surgical release of the nerve, etc.).
  • Compression neuropathy, i.e. peripheral nerve compression, is caused by external pressure on the nerve that is often a one-time occurrence (e.g. a night's drunken sleep with the upper arm pinched), or occasionally intermittent (e.g. leaning on the elbow while speaking on the telephone).
    • Compression neuropathy usually recovers spontaneously once the external pressure is removed.

Symptoms of nerve entrapment and compression

Sensory nerve symptoms

  • Peripheral nerve entrapments are common causes of sensory symptoms.
  • Numbness, stinging or tingling sensations, increased or decreased sensation and pain. Symptoms are usually more disturbing at night (wake up from sleep).
  • Sensory symptoms usually occur distal to the entrapment; however, they may be referred all the way to the root level (e.g. carpal tunnel syndrome → neck pain).

Motor nerve symptoms

  • Less often there is also muscle weakness and clumsiness or atrophy in the muscles supplied by the compressed nerve, distal to the site of the entrapment, if the condition remains untreated for a long time.
  • In entrapment neuropathy, the motor nerve symptoms require timely surgical treatment, because muscle atrophy is usually irrevocable.
  • Tinel's sign
    • The site of the nerve lesion is tender when palpated; tapping it causes a distally radiating sensation.
    • As the compression is released, the site where Tinel's sign is elicited moves distally along the nerve. This will assist in assessing the prognosis after the release.

Most common disorders caused by nerve entrapment and compression

  • Compression is most likely to injure nerves that have no surrounding protective soft tissue.
  • Most common disorders caused by nerve entrapment and compression
    • Carpal tunnel syndrome
    • Cubital tunnel syndrome in the area of the elbow joint
    • Compression paresis of the radial nerve
    • Entrapment of the ulnar nerve at the wrist
    • Peroneal paresis
  • Other conditions caused by nerve entrapment and compression are evidently more rare.

Medial nerve

Entrapment at wrist level (carpal tunnel syndrome)

  • See Carpal Tunnel Syndrome (CTS).
  • Typically a middle-aged female who uses her hands at work a great deal.
  • Symptoms and clinical findings
    • Numbness in the thumb, index and middle fingers (possibly also ring finger), weakness and clumsiness of thumb opposition
    • A typical symptom is night-time numbness of the upper limb.
    • Occasionally sensory symptoms extending all the way to the neck
    • Often bilateral, even when symptoms are unilateral.
  • Treatment is conservative or operative, see Carpal Tunnel Syndrome (CTS).

Nerve entrapment at the proximal end of the forearm below the pronator muscle (pronator syndrome)

  • An over-diagnosed rarity
  • Symptoms and clinical findings
    • As above; in addition, the pain is provoked and radiates distally at resisted pronation of the forearm.
    • Occasionally flexion of the elbow and wrist is also weak.

Ulnar nerve

Entrapment of the ulnar nerve at the condylar groove (cubital tunnel syndrome)

  • Symptoms and clinical findings
    • Sensory symptoms in the ring and little fingers
    • Weak flexion of ring and little fingers
    • Weak scissors movement
  • If the symptoms are caused by luxation of the ulnar nerve from the groove when the elbow joint is flexed, the symptoms are provoked and the luxation can be palpated or felt when the elbow joint is flexed.
  • Simple decompression is the treatment of choice Surgical Management of Ulnar Nerve Compression at the Elbow.

Entrapment at wrist level (ulnar tunnel syndrome)

  • Symptoms and clinical findings
    • As above, ring and little fingers
    • Weak scissors movement

Entrapment in the hollow of the palm (the motor branch leading to the first interosseal muscle)

  • Rare; typical history includes, e.g. floor-tile work, competitive bicycling, local injuries
  • More often a local compression injury than a true entrapment.
  • Symptoms and clinical findings
    • Weak adduction of thumb and index fingers, pain in the region of the ulnar metacarpal bones
    • No sensory impairment

Radial nerve

Compression posteriorly in the humerus ("Saturday night palsy")

  • Alcohol is a contributing factor (sleeping on the hand/arm).
  • Symptoms and clinical findings
    • Weakness or paresis in extension of wrist and fingers
    • Sensory symptoms on the radial side of the back of the hand
    • Extension of the elbow joint is usually normal.
  • Treatment
    • Usually spontaneous recovery with monitoring over a few months
    • Failing the above, consider further consultation.

Entrapment at the proximal end of the radial nerve below the supinator muscle (supinator syndrome)

  • Ca. 1% of clinical suspicions are actually confirmed; the symptoms are mostly caused by local tendinitis or other painful conditions.
  • Symptoms and clinical findings
    • Weakness in extension of wrist and fingers with normal sensations

Common peroneal nerve

Distention or compression at the end of the fibula

  • E.g. in berry pickers or alcoholics
  • Symptoms and clinical findings
    • Sensory symptoms on the anterior side of the lower leg and over the metatarsal area.
    • Paresis or weak dorsiflexion of ankle and foot.
    • The foot is dangling, gait consists of short steps, the patient cannot walk on his/her heels.
  • Treatment
    • Generally spontaneous recovery with possible monitoring over a few months
    • Failing the above, consider further consultation.
  • Note: Should be differentiated from the L5 root symptoms.

Posterior tibial nerve

Entrapment at the level of the medial malleolus (tarsal tunnel syndrome)

  • Symptoms and clinical findings
    • Sensory impairment in the plantar area, pain in the plantar and medial malleolar area
    • Motor nerve symptoms are rare: atrophy of small plantar muscles.
    • Rising on tiptoe is difficult.

Lateral femoral cutaneous nerve

Entrapment at the inguinal ligament ("meralgica paresthetica") Treatment for Meralgia Paraesthetica

  • See Meralgia Paraesthetica.
  • Frequently nerve irritation without an actual entrapment (symptoms are not persistent).
  • Symptoms and clinical findings
    • Exclusively sensory symptoms
    • Burning pain and numbness on the lateral side of the thigh
  • Treatment
    • Weight-loss programme, avoidance of tight clothing
    • Injection of glucocorticoid + local anaesthetic into the medial area of the lateral attachment site (about two centimeters medially and slightly caudally from the anterior superior iliac spine)
    • In persistent cases, the treatment is surgical release of the nerve, or neurolysis.

Diagnostics of nerve entrapments and compression

  • Electroneuromyography (ENMG) is a necessary addition to the clinical tests when the compression neuropathy does not seem to resolve as expected, or when surgical treatment of the entrapment neuropathy is being considered. This will also reveal polyneuropathy, which increases the risk of nerve injury.
  • In hereditary neuropathy with liability to pressure palsies (HNPP) the patient suffers from recurrent, usually spontaneously recovering nerve damages. Predisposing factors include e.g. nerve stretching, injury or local compression effect.
  • Specialist consultation is always advisable when the clinical symptoms of nerve damage are atypical.
  • The decision to operate on an entrapped nerve should be made by an expert in the field.

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